Bounce Back after Impact
Bounce Back after Impact
(OP)
I need help calculating the amount a rotating output shaft will bounce back after hitting a hard stop. The inertia of the rotating element is 4.85 E-04 oz-in-sec^2. This inertia is rotating at a speed of 2300 rad/sec. Between the load inertia and the hard stop is a torsion spring that has an overall spring constant of 7.3E6 oz-in/rad. The spring constant of the hard stop is 11.3E9 oz-in/rad and it appears to be structurally capable of withstanding the impact. Once the impact occurs, there is no damping or friction present in the system to limit the bounce back.





RE: Bounce Back after Impact
Your best bet is to do it empirically with test data.
It is insufficient to say that there is no loss of energy after impact. The problem is what is the loss during impact.
RE: Bounce Back after Impact
TTFN
RE: Bounce Back after Impact
I made a mistake in my original question. We measured about 4 in-oz of friction in the system. In the past, we have analyzed impacts like this by setting the KE of the rotating element equal to the PE of the "hard stop" (usually made up of springs). This allows you to define a suitable spring constant for the "hard stop" so that all the energy can be absorbed over a specific amount of spring deflection. In most cases we use brakes to stop the rotating element just after the impact occurs. This limits the "bounce back". In this case, the rotating element is free to rebound.
RE: Bounce Back after Impact
RE: Bounce Back after Impact
RE: Bounce Back after Impact
That means that the 2*compression*friction is the only significant energy loss mechanism
TTFN
RE: Bounce Back after Impact
This is an extremely documented problem in first year mechanics textbooks.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Bounce Back after Impact
Anyway, the easiest thing to do is to set up a numerical solution in Excel.
Cheers
Greg Locock